Arc extinguishing device



Feb- 1, 1949 w. A. ATWOOD ET AL.

ARC EXTINGUISHING DEVICE Filed 0G13. 8, 1945 Inventors. Wirwfielcl AAM/voed EU @ne VLoehrwe,

The'nA Attofrw ey.

Patented eb. l, 1949 ARC EXTINGUISHING DEVICE Winfield A. Atwood, Yeadon, and Eugene W. Boehne, Drexel Hill, Pa., assignors to General Electric Company, a corporation of New York Application October 8, 1945, Serial No. 621,064

2 Claims. 1

Our invention relates to improvements in arc extinguishing devices and more particularly to arc extinguishing devices for circuit breakers and especially circuit breakers for interrupting unidirectional currents having a high rate of rise.

Since unidirectional currents do not periodically pass through zero values as do alternating currents, the problem of circuit interruption is more difficult and especially so with so-called anode circuit breakers used in controlling arc rectiiiers because of the high rate ofvrise of current when an arc-back occurs. Arc extinguishing devices for such circuit breakers are therefore subject to severe duty. Since vaporized metal in the arc stream tends to maintain and stabilize the arc, it is necessary to keep the metal vapor in the arc at a minimum. The metallic content of the arc stream is dependent Yprincipally upon metal derived from the arc runners. It is therefore important that the ends of the arc in contact with the arc runners be kept moving continuously in order to avoid heat concentration and the consequent high vaporizing action and also that arc runners be made of metal having a high melting temperature. Inasmuch as arcs effect a vaporizing action of the materials used in the construction of an arc extinguishing device and in consequence of the high velocities of the gases generated also effect an eroding action of the parts, such action should be controlled insofar as possible in such a way as to expedite arc extinction and to minimize the damage to the parts.

An object Vof our invention is to provide an improved arc extinguishing device in the form of an arc lengthening chute wherein the vaporizing action of the arc on the arc runner parts ofthe device is minimized and what there is of such action is so controlled as to assist in the ex`- tinction of the arc. Another object of our invention is to provide an improved arc extinguishing chute wherein the extinction of the arc is expedited by the pressure expelling action of gases conned to recidivous arcing pockets provided in the chute for oscillating the ends of the arc at the outwardly hooked ends of the arc runners.

Still another object of our invention is to provide an improved arc extinguishing chute which is readily removable vfrom the circuit breaker and which, although compact and relatively small, has high interrupting capacity. A further object of our invention is to cool the main portion of the arc particularly while keeping the ends of the arc rapidly moving to the ends of the arc runners. These and other objects of our invention will appear in more detail hereinafter.

In accordance with our invention, we provide an improved arc extinguishing chute wherein divergent arc runners of high melting point electric current conducting material have their outer or discharge ends curved around into the recidivous arcing pockets formed in the arc chute to prevent the ends of the arc from becoming consequence of the arc current flowing therein.

Further in accordance with our invention, the arc extinguishing chute is provided with suitable arc cooling means which divide the chute into several relatively thin intercommunicating chambers.

Our inv-ention will be better understood from the following description when considered in connection with the accompanying sheet of drawings, and its scope will be pointed out in the appended claims.

In the accompanying drawing, Fig. 1 is a side elevation of an arc extinguishing device embodying our invention with parts removed for clearness of illustration; Figs. 2, 3, 4 and 5 are sectional views on the lines 2 2, 3 3, 4 4, and 5 5, respectively, of Fig. 1; Fig. 6 is an outline diagram illustrating an actual arc discharge in a device embodying our invention; and Fig-'7 is a perspective view of a detail of the illustrated embodiment of our invention.

As shown in Fig. 1, we have illustrated an emv bodiment of our invention as applied to a circuit breaker such as that disclosed in Letters Patent of the United States 2,329,003, issued September 7, 1943. Since the circuit breaker itself forms no part of our invention, only such parts f the cir- 3 tact 3 is a movable arcing contact 5. Both the movable main contact 4 and the arcing contact 5 are electrically connected to the lower terminal stud 6 of the circuit breaker by suitable means including a flexible lead 1. The circuit breaker 'is shown as supported on va base 8 of suitable inf sulating material.

In accordance with our invention, we provide an improved arc extinguishing chute which is adapted to be mounted on the circuit breaker adjacent to and principally above the arcing contacts 3 and 5. As shown, this chute comprises two spaced plates 9 and III of suitable insulating material for enclosing the arcs drawn between the contacts 3 and 5 upon separation thereof. In Fig. 1, the plate 9 has been removed in order more clearly to show the interior construction of our arc extinguishing chute. As shown, the outline of the plates 9 and III is that of a rectangle having a portion of generally trapezoidal form adjoining its lower edge. The arc chute thus has relatively large and small exhaust and arc initiating openings respectively, that is, a relatively small opening where the arc is initiated when the contacts 3 and 5 are separated at the entrance of the chute and a relatively large opening where the arc is discharged.

Between the plates 9 and I0 and along the lower front and back edges thereof, we provide insulating spacing side walls comprising as shown a series of abutting members such as blocks or diverging strips II and I2 of suitable insulating material and the curved side wall extension elements I3 and I4 also of suitable insulating material which together with the abutting side wall extension elements 29 form a pair of reversed J-shaped side wall extension elements abutting the diverging strips II and I2 behind the divergent ends thereof. In the illustrated embodi ment of our invention, the insulating side wall strip members II and I2 are positioned between the plates I9 and I0 in an upwardly divergent relation so as suitably to support 'the divergent arc runners I and I6 thereon which constitute arcing surfaces on the strips II and I2, respec-k tively. In order to eliminate vgas pockets and to prevent burning of parts behind the arc runner I5 when the circuit breaker is opened while carrying current, we provide ller pieces II' of suitr able insulating material which are suitably secured to the sides of the strip I I al1 as shown more clearly in Fig. 7. For protecting the side plates 9 and I0 against the eroding action of the arc terminal as it travels along the arc runner I6, protective plates I'I of high arc resistant insulating material are positioned between the plates 9 and II) and the block I2. The arc runner mounting strip I2 is held in assembled position with the protective plates I1 and the `side rplates 9 and I0 by suitable fastening means such as bolts I8 which pass through suitable insulating bushings I9. The rear side wall block and arc runner support II is mounted on the upper stud I and secured thereto by suitable means such as bolts and to the base 8 by bolts 2l which also assist in holding the arc runner I5 in position on the block I I. The arc runner I6 is secured to theiy block I2 by suitable means such as flat-headed countersunk screws, not shown. The rear side wall extension element I3 abuts a shoulder II on the arc runner mounting strip II and the llers II' secured thereto and rests on the base ner mounting strip I2 is notched to receive the ends of the side wall extension element I4 in abutting engagement against a sealing piece of high arc resistant insulating'material 22. As shown, the lower end of the arc runner I 5 carries the stationary arcing contact 3. The lower end of the arc runner I3 is bent around the lower end of the arc runner mounting strip I2 and has secured thereto a terminal strap 23 to which is connected, as shown ln Fig. 4, a suitable'lead 24. The lower edge of the plate I0 is provided with a semi-circular notch III' to admit the strap 23. The/lower end of the lead 24 is connected to the lower stud 6 of the circuit breaker. In order to avoid confusing the drawing, this lead is not shown in Fig. 1.

In accordance with our invention, the side wall abutting members II, I2, I3 and I4 are so shaped and arranged as to formreversely curved recidivous arcing pockets 25 and 26, shown in Fig. 1, in the arc chute for receiving the outwardly hooked ends of the arc runners I6 and I5, respectively. For this purpose, the'upper edges of the side wall extension elements I3 and I4 may be curved concave upwardly and the upper or divergent ends of the spacer blocks II and I2 arranged to overlap the reversed hook-shaped ends of the elements I3 and I4. Further in accordance with our invention, the upper ends of the divergent arc runners I5 and i6 are outwardly curved in the form of a hook around the upper or divergent ends of the runner mounting strips II and I2, respectively, into the recidivous arcing pressure pockets 26 and 25, respectively. As

" shown, the extent of this hook curvature at the end of the arc runners is about 180, butin general the extent of the outward curvature is governed by the inclination of -the divergent arc' runner to the horizontal. Stated more specilically, we find that the hook curvature should be at least suicient to extend materially beyond the point of tangency ofv the arc runner with a vertical'line at the end thereof.' When the circuit breaker opens while carrying current of substantial magnitude the arc before breaking is forced to travel the entire length of the arc runner and the arc end or terminal is driven over the hooked end of the arc runner into the undercurving pocket nesting the end thereof. Ionized gases are thus trappedinside the pocket where they expand and are then expelled to form a low resistance path at the entrance to the pocket. In consequenceof this, while other/portions of the arc are being extended in length toward the r breaking point, the arc terminal usually does not remain at the extreme end of the arc runner but reattaches itself to the runner above the extreme end. This action is repeated so that each time the are thus reattaches itself, its terminal tends to be driven repeatedly along the curved -portion to the extreme end 'of the runner and then back again thus oscillating the running end of the arc into and out of the recidivous arcing pocket to avoid the heating of individual spots with the consequent deterioration of therunner. Each time the action is repeated, gas pressure is built up in the recidivous arcing pocket nesting the end ofthe arc runner until the total arc. length is so increased that the discharge of the arc products is effected atthe top of the arc chute under the accelerating action of the builtup pressure.

8 to maintain the arc extinguishing device in A In order to minimize the metallic content of the arc products and also to move the arc upwardly in the arc compartment without the use of blowout coils and the like, the arc runners I5 and I6 are preferably made of a high melting point magnetic material such as iron or steel. Under these conditions, the reaction between the flux field of the are and the flux fields of the runners I 5 and I6 causes the arc to travel upward in the arc compartment.

In order to provide better -cooling of the arc and the arc products, we provide in the arc chute between the outside plates 9 and I0 a plurality of spaced arc splitters 21 which extend downward from the top of the arc chute into the notch between the divergent arc runners I5 and I6 to varying depths, as indicated more clearly in Fig. 2. For greater cooling action and' production of parallel arc paths, the arc splitters 21 are preferably perforated as indicated at 28. At the front and back edges of the arc chute, the spaces between the splitters 21 and between the splitters 21 and the plates 9 and I0 are closed by insulating side wall extension 29 which together with the reversely curved abutting elements I3 and I4 form the reversed hook-shaped side wall extensions that abut the runner mounting strips II and I2 behind the divergent ends thereof. In the adjoining edges of the side wall extension elements 29, the splitters 21 and the spacers I3 and III, notches are provided for the reception of a sealing strin 30 of high arc resistant insulating material. For maintaining the rigidity and assembly of the parts' of the arc chute, we provide longitudinal braces 3| and an interlocking transverse brace 32 on the outside of each of the plates 9 and I0. These-braces are bolted together with the plates 9 and I0, the spacers 29 and splitters 21 by suitable means such as bolts 33. The braces 3| and 32 are preferably made of some non-frangible insulating material such as impregnated laminated wood or the like. Those bolts which pass through the splitters 21 where there are no other spacers are provided with insulating bushings 34.

Assuming the arcing contact 5 to move away from the arcing contact 3 during the opening of the circuit breaker under an overcurrent condition, for example, then an arc is formed between the contacts 3 and 5 and the end of the arc attached to the movable contact 5 is quickly transferred to the arc runner I6. Under the magnetic reaction of the flux iield due to the arc and the flux iields created by arc current ilow in the runners I5 and I6, the arc is caused to move rapidly upward in the chute with its ends traversing the curved portions of the arc runners I5 and I6. At the same time, by virtue of the arc splitters 21, the arc is formed into two or more parallel branches in consequence of the intercommunicating compartments between the splitters and the plates 9 and. I0. These arc branches are in consequence more rapidly cooled than the whole arc from which they were derived would be cooled. With the ends of the arc 0n the curved portions of the arc runners and arc reformation at these points, gases are rapidly evolved in the recidivous arcing pockets 25 and 26 to build up pressures which are highly eiective in blowing out or discharging the arc products at the top near the front and back of the arc chute. Thus, referring to Fig. 6 wherein the arc chute is simply outlined, the dashdot line indicates the outline of the discharged incandescent products of the arc as actually photographed during a circuit breaker interruption. From the nodes 36 and 31 of the curved outline of the arc discharge indicated by the line 35 in Fig. 6, the expulsive action of the gases formed under pressure in the pockets 25 and 26 will be obvious. In other words, in consequence of the rapid -travel of the ends of the arc into the pockets 25 and 26 where the vaporizing action is more or less highly concentrated to build up pressure quickly, the arc discharge products are violently expelled from the arc chute near the edges thereof, whereas the central or body por- .tion of the arc is less violently expelled as will be clear by the central portion 35.

While we have shown and described our invention in considerable detail, we do not desire to be limited to the exact arrangements shown, but seek to cover in the appended claims all those modifications that fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In an arc extinguishing device, two insulating plates forming an arc lengthening chute, insulating side walls between said plates comprising two hook-shaped elements in reverse spacedapart alignment and two strips extending divergently outward from the arc initiating portion of the chute toward the discharge portion 'thereof and into abutting engagement with the inwardly curved ends of said hook-shaped ele ments with the ends of the strips projecting therebeyond in the chute to form therein recidi- Vous arcing pockets open toward the discharge portion of the chute, and two divergent arc runners in said compartment respectively mounted cn said strips, each of said arc runners having an outwardly hooked end curved around the projecting end of the mounting strip therefore into the recidivous arcing pocket therebehind.

2. An arc extinguishingdevice having in cornbination an arc chute provided with a pair of opposing plates having divergent side wall members mounted therebetween and each provided with a side wall extension joined behind the divergent end of the corresponding side wall member to form a recidivous arcing pocket opened towards the discharge end of the chute, and a pair of divergent arc runners of vaporizable conducting material, each mounted on the inner side of a corresponding one of the divergent side wall members and having the end of the runner hooked around the divergent end of themember into the recidivous arcing pocket for oscillating the arc into and out of the pocket and thereby minimize vaporization at the hooked end of each runner.

WINFIELD A. ATWOOD. EUGENE W. BOEHNE.

REFERENCES CITED The following references are of record in the nie of this patent:

UNITED STATES PATENTS Number Name Date 1,519,230 Aalborg Dec. 16, 1924 1,606,808 Riley Nov. 16, 1926 1,614,173 Aspinwall Jan. 11, 1927 1,614,176 Austin Jan. 11, 1927 1,722,165 Watson July 23, 1929 1,836,994 Slepian Dec. 15, 1931 1,934,518 Anderson Nov. 7, A1933 1,957,480 Van Emden May 8, 1934 2,100,743 Johnson Nov. 30, 1937 2,311,690 Pokorny Feb. 23. 1943 

